1. Field of the Invention
The present invention relates to a liquid crystal display device, and in particular to a liquid crystal display device which is suitably used for a mobile electronic device. The present invention also relates to a mobile electronic device incorporating such a liquid crystal display device, and a substrate for use in such a liquid crystal display device.
2. Description of the Related Art
In recent years, mobile electronic devices such as mobile phones and PDAs (Personal Digital Assistants) are in wide use. In a display section of a mobile electronic device, a liquid crystal display device is frequently used because of its advantages in terms of thinness, light weight, and low power consumption.
A liquid crystal display device is a non-emission type display device, and therefore includes an illuminator (called a backlight) so that light from the backlight is utilized in performing display. A backlight is generally composed of a light source, a reflection plate, a light guiding plate, a lens sheet, and the like. Since the thickness of a backlight greatly affects the overall thickness of the liquid crystal display device, a thin backlight must be used in order to realize a thin liquid crystal display device.
Backlights are generally classified into “direct type” backlights (such as that which is disclosed in Japanese Laid-Open Patent Publication No. 2003-215585) and “edge light type” backlights (such as that which is disclosed in Japanese Laid-Open Patent Publication No. 8-94844). A “direct type” backlight includes, as shown in FIG. 23, a plurality of light sources 702 (such as cold-cathode tubes) which are disposed immediately under a liquid crystal display panel 701. On the other hand, an “edge light type” backlight includes, as shown in FIG. 24, a light source 802 disposed on a side edge of a light guiding plate 803, which in itself is provided immediately under a liquid crystal display panel 801, such that the light from the light source 802 is led to the liquid crystal display panel 801 by the light guiding plate 803.
Since an edge light type backlight can be made thin more easily than a direct type backlight, edge light type backlights are currently used in many small-sized liquid crystal display devices.
However, liquid crystal display devices are required to become even thinner due to the recent explosive prevalence of mobile electronic devices. Such needs cannot be satisfied by conventional edge light type backlights.